Dechlorination of haloethanes using ethylene

ABSTRACT

A haloethane is dechlorinated by reacting in the gaseous phase a haloethane selected from CCl 2  FFCClF 2 , CClF 2  CClF 2  and CCl 2  FCCl 2  F with ethylene in the presence of a transition metal catalyst selected from iron, nickel, vanadium and chromium oxides, chlorides and fluorides and recovering a perhaloethylene and vinyl chloride. Perhaloethylenes are used as monomers for halogenated polymers. Vinyl chloride is also a widely used monomer.

BACKGROUND OF THE INVENTION

Perhaloethylenes such as monochlorotrifluoroethylene or tetrafluoroethylene are presently prepared by dechlorination of the corresponding haloalkenes such as 1,1,2-trichloro-1,2,2-trifluoroethane or 1,2-dichlorotetrafluoroethylene with zinc metal in alcohol. Suggestions have been made to dechlorinate with hydrogen or hydrogen supplying materials in the vapor phase, with another haloalkene and reduced salt melts as the chlorine acceptor.

The present zinc process consumes expensive zinc and gives a moderate product yield. The various proposed processes either consume expensive materials, give low conversion or both.

BRIEF DESCRIPTION OF THE INVENTION

The invention includes a method for the dechlorination of haloethanes comprising reacting in the gaseous phase a haloethane selected from the group consisting of CCl₂ FCClF₂, CClF₂ CClF₂ and CCl₂ FCCl₂ F with ethylene in the presence of a transition metal catalyst selected from the group consisting of iron, nickel, vanadium and chromium oxides, chlorides and fluorides and recovering a perhaloethylene and vinyl chloride.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is concerned with a process for the alpha, beta dechlorination of a haloethane by reaction with ethylene in the presence of a catalyst. Preferred halohydrocarbons include 1,2-dichlorotetrafluoroethane (known as fluorocarbon 114) and 1,1,2-trichloro-1,2,2-trifluoroethane (known as fluorocarbon 113). When two chlorines are removed from these preferred halohydrocarbons, the product perhaloethylenes are tetrafluoroethylene (fluorocarbon 1114) and chlorotrifluoroethylene (fluorocarbon 1113), which are important fluoropolymer monomers. Fluorocarbon 112 may also be converted to fluorocarbon 1112.

Using ethylene as the other reactant the byproducts are vinyl chloride, itself useful as a polymer monomer, and HCl. The byproduct HCl may add across one of the double bonds of product or byproduct vinyl chloride. Ethylene may also be directly converted to 1,2-dichloroethane. However, under most reaction conditions, any 1,2-dichloroethane formed in situ is converted to vinyl chloride by HCl elimination.

The temperature of the reaction is not critical, with various combinations of catalyst, haloethane and ethylene exhibiting different temperature ranges for some reaction rate and for maximum reaction rate. Obviously, in order to have reaction in the gaseous phase, the temperature and pressure must be such that all reactants are in the vapor phase. Also, clearly, temperatures at or above the decomposition temperatures of reactants and products cannot be used. Preferred temperatures, especially for the reaction between ethylene and fluorocarbon 113 or 114, are between about 400° C. and about 600° C. with between about 400° and about 500° C. being more preferred and between about 450° C. and about 500° C. being most preferred.

The pressure of the reaction is not critical, although substantially atmospheric pressures are preferred. The molar ratio of haloethane:ethylene is not critical but is preferably between about 0.1:1 and about 10:1 with between about 0.5:1 and about 2:1 being more preferred.

The contact time is not critical so long as the reactants are in contact with the catalyst sufficiently long for reaction to occur. Contact times of about 0.3 to about 60 seconds are preferred since little yield improvement is likely to occur with greater contact times, and more preferred contact times are between about 3 and about 6 seconds.

The catalyst must be a transition metal oxide or halide which actively catalyzes the present reaction. As shown in the examples that follow, a broad range of materials are somewhat active. The catalysts of the present invention which are especially active include oxides, fluorides and chlorides of iron, nickel, vanadium and chromium. They may be applied to an inert support, as for example at a rate of between about 0.003 and about 0.30 moles of oxide, fluoride or chloride per 100 grams of support. By "inert" is meant that the support is not significantly decomposed under reaction conditions which normally includes some HF from side reactions. The support may itself have catalytic activity, as for example magnesium chloride or fluoride supports, or may include promoter materials such as alkali halides. Materials such as alpha or gamma alumina are less preferred as supports since they do react with HF to an extent.

The preferred catalyst materials includes oxides such as iron (II) oxide, iron (III) oxide, nickel (II) oxide, vanadium (II) oxide, and chromium (III) oxide. They also include chlorides such as iron (II) chloride, iron (III) chloride, nickel (II) chloride, vanadium (IV) chloride, vanadium (II) chloride, chromium (III) chloride and chromium (II) chloride and the corresponding fluorides. Preferred catalyst also include oxychlorides and oxyfluorides such as CrOF, FeOCl and the like, which represent partially fluorinated or chlorinated oxides.

More preferred are the iron compounds at valence state 3, including iron (III) oxide, iron (III) chloride and iron (III) fluoride, as well as partially chlorinated or fluorinated oxides. Most preferred is iron (III) chloride.

Especially preferred combinations of catalyst and support include iron (III) chloride on sodium magnesium fluoride, iron (III) chloride on potassium magnesium fluoride, iron (III) chloride on gamma aluminum fluoride and iron (III) chloride on chromium (III) oxide.

COMPARATIVE EXAMPLE 1

0.3 moles of copper (II) chloride is applied to 100 grams of Al₂ O₃ support particles of 10-20 mesh size (American standard mesh size), by dissolving the chloride in about 50 milliliters of water and adding the solution to an evacuated flask containing the support particles. The sample was then dried overnight at 100° C. A 100 milliliter portion of the sample was charged to a three-fourths inch inside diameter, 20 inch long stainless steel reactor immersed in a temperature controlled sand bath at 400° C., 450° C. and 500° C. 1.44 moles/hour of ethylene and 0.72 moles/hour of trichlorotrifluoroethane (fluorocarbon 113 or CCl₂ FCClF₂) were fed into the reactor giving a contact time of 3.3 seconds. After one hour, the effluent was analyzed by on-line gas chromatography. The results are shown in Table 1 indicating a greatest conversion of fluorocarbon 113 at 500° C. (58%) with 72% of the reacted 113 going to C₂ ClF₃ (fluorocarbon 1113) and 0.64 being the ratio of vinyl chloride/fluorocarbon 1113.

EXAMPLES 2-10

Example 1 was repeated using each of the chlorides on an Al₂ O₃ base shown in Table 1. Conversion of fluorocarbon 113 was highest in Example 6 for iron (III) chloride (98%) with 95% yield and a ratio of 0.36. Examples 2, 3, 6 and 7 represent the use of catalysts of the present invention. The remainder (designated C for comparative) represent other catalyst materials.

                  Table 1                                                          ______________________________________                                         Reaction of C.sub.2 ClF.sub.3 and C.sub.2 H.sub.4                              Contact Time 3.3 Seconds                                                                               % Conver-                                              Ex-             Temp-   sion*   % Yield**                                      ample Catalyst  erature of C.sub.2 Cl.sub.3 F.sub.3                                                            C.sub.2 ClF.sub.3                                                                      Ratio***                               ______________________________________                                         Cl    Copper (II)                                                                              400     9       53      0.50                                         chloride on                                                                              450     30      71      0.30                                          Al.sub.2 O.sub.3                                                                        500     58      72      0.64                                   2     Chromium  400     6       48      0.17                                         chloride on                                                                              450     23      71      0.35                                          Al.sub.2 O.sub.3                                                                        500     41      92      0.42                                   3     Nickel    400     20       8      0.70                                         chloride on                                                                              450     43      32      0.57                                          Al.sub.2 O.sub.3                                                                        500     50      85      0.24                                   C4    Manganese 450     36      71      0.18                                         chloride on                                                                     Al.sub.2 O.sub.3                                                        C5    Cobalt    400     15       8      0.69                                         chloride on                                                                              450     35      89      0.07                                          Al.sub.2 O.sub.3                                                                        500     29      88      0.17                                   6     Iron      400     48      41      0.85                                         chloride on                                                                              450     83      71      0.50                                          Al.sub.2 O.sub.3                                                                        500     98      95      0.36                                   7     Vanadium  400     7       24      0.00                                         chloride on                                                                              450     38      81      0.46                                          Al.sub.2 O.sub.3                                                                        500     86      93      0.05                                   C8    Palladium 400     7       75      0.13                                         chloride on                                                                              450     30      85      0.06                                          Al.sub.2 O.sub.3                                                                        500     42      87      0.05                                   C9    Cerium    400     5       42      0.08                                         chloride on                                                                              450     24      82      0.21                                          Al.sub.2 O.sub.3                                                                        500     90      81      0.07                                   C10   Zinc      400     5       68      0.00                                         chloride on                                                                              450     39      80      0.03                                          Al.sub.2 O.sub.3                                                                        500     90      81      0.07                                   ______________________________________                                          *By "% Conversion" is moles C.sub.2 Cl.sub.3 F.sub.3 consumed/moles            C.sub.2 cl.sub.3 F.sub.3 fed × 100.                                      **By "% Yield" is means moles C.sub.2 ClF.sub.3 produced/moles C.sub.2         Cl.sub.3 F.sub.3 consumed × 100.                                         ***By "Ratio" is meant moles C.sub.2 H.sub.3 Cl produced/moles C.sub.2         ClF.sub.3 produced.                                                      

EXAMPLES 11-32--10 SECOND CONTACT TIME

Example 1 was repeated for the catalysts shown in Table II with the feed rates slowed down to 0.48 moles/hour for ethylene and 0.24 moles/hour of fluorocarbon 113 giving a contact time of 10 seconds. The results are displayed in Table II. It should be noted that the γAlF₃ of Example 22 was prepared by fluorinating Al₂ O₃ with HF at below 420° C. while the αAlF₃ of Example 23 was prepared by fluorinating Al₂ O₃ with HF at about 720° C. The supports of Examples 30, 31 and 32 were obtained from Girdler Chemical, Inc. of Louisville, Kentucky. Examples 14, 15, 16, 17, 20, 22, 23, 25 and 28 represent the present invention. The remaining examples (designated C) are comparative examples.

                  Table II                                                         ______________________________________                                         Reaction of C.sub.2 Cl.sub.3 F.sub.3 And C.sub.2 H.sub.4                       Contact time 10 Seconds                                                                                   % Conver-                                           Ex-                Temp-   sion    % Yield                                                                               Ra-                                  ample Catalyst     erature of C.sub.2 Cl.sub.3 F.sub.3                                                            C.sub.2 ClF.sub.3                                                                     tio                                  ______________________________________                                         C11   Sodium       400     3       69     0.00                                       chloride on  450     33      73     0.26                                       Al.sub.2 O.sub.3                                                                            500     74      85     0.30                                 C12   Al.sub.2 O.sub.3                                                                            400     16      21     0.51                                       alone        450     39      47     0.33                                                    500     61      93     0.14                                 C13   Copper (II)  400     8       70     0.10                                       chloride on  450     27      79     0.25                                       Al.sub.2 O.sub.3                                                                            500     63      85     0.37                                 14    Iron (III)   400     11      53     0.12                                       chloride on  450     32      58     0.34                                       NaMgF.sub.3  500     69      80     0.44                                 15    Nickel (II)  400     2       91     0.30                                       chloride on  450     17      68     0.10                                       NaMgF.sub.3  500     50      79     0.23                                 16    Vanadium     400     4       71     0.00                                       chloride on  450     57      95     0.04                                       NaMgF.sub.3  500     62      81     0.35                                 17    Iron (III)   400     20      84     0.27                                       chloride and 450     27      80     0.35                                       potassium    500     68      84     0.38                                       chloride on                                                                    NaMgF.sub.3                                                              C18   NaMgF.sub.3  400     4       60     0.00                                       alone        450     28      50     0.19                                                    500     50      74     0.43                                 C19   Copper (II)  400     10      73     0.05                                       chloride on  450     43      63     0.31                                       KMgF.sub.3   500     84      87     0.62                                 20    Iron (III)   400     10      73     0.05                                       chloride on  450     43      63     0.31                                       KMgF.sub.3   500     84      87     0.62                                 C21   Copper (II)  400     7       51     0.11                                       chloride on  450     12      100    0.00                                       carbon       500     24      86     0.07                                 22    Iron (III)   400     35      69     0.61                                       chloride on  450     49      76     0.57                                       AlF.sub.3    500     46      90     0.39                                 23    Iron (III)   400     3       56     0.07                                       chloride on  450     10      82     0.18                                       AlF.sub.3    500     44      82     0.33                                 C24   Copper (II)  400     54      82     0.08                                       chloride on                                                                    Cr.sub.2 O.sub.3                                                         25    Iron (III)   400     29      83     0.10                                       chloride on  450     55      87     0.32                                       Cr.sub.2 O.sub.3                                                         C26   Cr.sub.2 O.sub.3                                                                            400     9       71     0.07                                       alone        450     29      81     0.06                                                    500     69      89     0.13                                 C27   Copper (II)  400     5       80     0.14                                       chloride on  450     15      81     0.54                                       NaF          500     26      87     0.12                                 28    Iron (III)   400     1       91     0.10                                       chloride on  450     6       96     0.25                                       NaF          500     20      93     0.14                                 C29   Copper (II)  400     39      30     0.55                                       chloride on  450     62      60     0.41                                       Girdler T-372                                                                               500     96      77     0.35                                       Refractory Oxide                                                         C30   Copper (II)  400     11      64     0.16                                       chloride on  450     34      86     0.24                                       Girdler T-373                                                                               500     78      88     0.56                                       Refractory Oxide                                                         C31   Copper (II)  450     10      87     0.20                                       chloride on  500     26      96     0.21                                       BaF.sub.2                                                                C32   Copper (II)  400     32      54     0.17                                       chloride on  450     81      79     0.48                                       Girdler mont-                                                                  morillonite clay                                                         ______________________________________                                     

We claim:
 1. A method for the dechlorination of haloethanes comprising reacting in the gaseous phase a haloethane selected from the group consisting of CCl₂ FCClF₂, CClF₂ CClF₂ and CCl₂ FCCl₂ F with ethylene in the presence of a supported transition metal catalyst selected from the group consisting of iron, nickel, vanadium and chromium oxides, chlorides and fluorides and recovering a perhaloethylene and vinyl choride.
 2. The method of claim 1 wherein said halohydrocarbon is CCl₂ FCClF₂.
 3. The method of claim 1 wherein said catalyst is selected from the oxides, fluorides and chlorides of iron at valence state
 3. 4. The method of claim 3 wherein said catalyst is iron (III) chloride.
 5. The method of claim 1 wherein said catalyst includes one of said oxides, fluorides or chlorides on an inert support, applied at a rate of between about 0.003 and about 0.30 moles of oxide, fluoride or chloride per 100 grams of support.
 6. The method of claim 5 wherein said catalyst is iron (III) chloride.
 7. The method of claim 6 wherein said support is gamma aluminum fluoride.
 8. The method of claim 6 wherein said support is alumina or partially fluorinated alumina.
 9. The method of claim 1 having contact time between about 0.3 and about 60 seconds.
 10. The method of claim 1 wherein said haloethane and ethylene are fed at a molar ratio of haloethane:ethylene between about 0.1:1 and about 10:1.
 11. The method of claim 10 wherein said ratio is between about 0.5:1 and about 2:1.
 12. The method of claim 1 where said haloethane is CClF₂ CClF₂.
 13. The method of claim 1 wherein the reaction is conducted at between about 400° C. and about 600° C.
 14. The method of claim 13 wherein the reaction is conducted at between about 400° C. and about 550° C.
 15. The method of claim 14 wherein the reaction is conducted at between about 450° C. and about 500° C. 